Correlation between lead retention and intestinal pinocytosis in the suckling mouse

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Abstract
Young animals absorb and retain a greater fraction of an oral dose of Pb than do adult animals. It has been proposed that pinocytotic activity in young animals is partially responsible for the increased Pb retention and absorption. Radiolabeled Pb (5 mg/kg) and polyvinylpyrrolidone (PVP, 50 mg/kg) were administered orally to 12-day-old suckling mice and to adult mice, and the uptake of Pb and PVP was determined periodically during a 6-day interval. Small intestines were removed, flushed clear of intraluminal contents, then divided into 24 segments of equal length for analysis. Intestinal tissue from the distal jejunum and ileum contained the greatest quantities of both Pb and PVP. Pretreatment of suckling mice with cortisone acetate resulted in decreased content of Pb and PVP within intestinal tissue, and decreased whole-body Pb retention. Cortisone pretreatment produced lower Pb concentrations in blood, brain, kidney and liver. Pretreatment with cortisone also reduced Pb absorption after intraluminal injection of Pb into the ileum. Pb and PVP uptake into intestinal tissue of adult mice was much less than uptake in suckling pups. Cortisone pretreatment of adult mice had no effect on whole-body Pb retention or intestinal tissue content of Pb or PVP. The correlation between pinocytotic activity and Pb retention supports the hypothesis that pinocytosis is 1 of the mechanisms involved in Pb absorption in suckling mice.